Memory loss with aging not necessarily permanent

Good news if you have those “where did I leave my keys?” senior moments: Scripps Research Institute scientists have found a way to reverse age-related memory defects in fruit flies by stimulating neurons — at least for “intermediate-term” memories (of smells paired with electrical shocks) lasting 30 min to several hours (in flies, which would be longer in humans).

Using optogenetic imaging*, the scientists learned exactly which neurons in the flies were associated with specific memories that were altered by aging to produce intermediate-term memory impairment.

Rescuing memories

Then they took it a step further: they placed either cold-activated or heat-activated ion channels in the neurons known to become defective with aging and then used cold, or heat, to stimulate them. In both cases, the intermediate-term memory was successfully rescued.

“This study shows that once the appropriate neurons are identified in people, in principle at least, one could potentially develop drugs to hit those neurons and rescue those memories affected by the aging process,” said Ron Davis, chair of the Department of Neuroscience at Scripps Florida.

“In addition, the biochemistry underlying memory formation in fruit flies is remarkably conserved (continues in DNA throughout evolution) with that in humans so that everything we learn about memory formation in flies is likely applicable to human memory and the disorders of human memory.”

* The researchers used transgenic (genetically modified) mice with the G-CaMP molecule expressed in neurons. G-CaMP is a “reporter” dye molecule that fluoresces (glows) whenever there is calcium influx (calcium flowing into a neuron), indicating that a neuron is active — in a conditioned response to a shock in this case). By exposing a fly to a specific smell and shining a laser beam at a neuron, they were able to determine (by seeing its fluorescent response in a confocal microscope) that this specific neuron was associated with a specific memory (of a shock). By repeating the test later, they could determine when the fly “forgot” the memory of the shock — and, after the rescue procedure, when the memory was restored.